You can't download SAP Server directly to your system untill you got SAP Certification.
There is two ways to access SAP SD(Sales & Distribution) from your system.
You can Install SAP IDES(International Demo Educational System) in your system.
To Install SAP IDES you need the below hardware requirements in your system.
Harddisk : 250 GB
RAM : 2 GB
If you are working in any organisation (or) Studying in any SAP Training institute ,Then you can install SAP GUI in your system and you will get the below details .
Application Server : XXX.XXX.XXX.XXX
Instance No : XX
System ID : XXX
Router String : XXXXXXXXXXXXXX
Thanks & Regards